1. Field of the Invention
This invention relates to a pneumatic valve assembly for controlling a stream of compressed air in response to a non-contacting actuation.
2. Description of the Prior Art
In pneumatic systems in which a signal is to be derived from a working piston it is known to accommodate said piston in a preferably stationary cylinder, which consists of non-magnetic material, and to provide the piston with a permanent magnet. By such an arrangement, by which reed relays and other sensors which are responsive to a magnetic field can be controlled, mechanical problems encountered in other pneumatic valves are alleviated. If such an arrangement is used to control a pneumatic main valve which controls pressures in the range from 1 to 8 bars, a magnetically actuated pneumatic signal generator must be provided for the control of the pneumatic main valve. Such an arrangement involves the disadvantage that a separate supply of compressed air under a pressure of less than 0.25 bar is required for the sensor and said air must have a high purity because otherwise the small orifices may easily be clogged under the low pressures applied. Besides, the known pneumatic sensors are susceptible to shock and continuously consume air at a rate of about 2 liters per minute.